the big concern now, hotspots flaring up overnight. >> reporter: scorching flames shot several feet into the air for hours. the intense fire created a large plume of thick, black smoke that could be seen for miles. from the north and east bays to sacramento, this is how it looked from sky four. fairfield fire investigators believe the fire was sparked after an employee ignited a plastic bin while working with possibly a torch or welder. >> they were working with an open flame object around the bins on the outside of the building. as far as i know, this is something in the normal course of their duties. we used water and a light foam all day long on the plastic bins. the foam helps to cool the fire. it's very effective in putting out fires from hydrocarbon based fuels. >> reporter: firefighters managed to contain the fire to 5 acres had the back lot. approximately 45 employees were working inside the plant at the time the fire broke out. all of them escaped unharmed. jose nunez is an employee and was scheduled to be at work at 4:00. >> it's a lot of fire everywhere, you know. yeah. i don'